Adding multilib support to Makefile in ../../.././libgcc
with_multisubdir=ppc64
Makefile:141: ../../gcc/libgcc.mvars: No such file or directory

It's off by one.

Please try this:

I thank you for looking in to this issue. However please forgive me,
but as a matter of fact,
the Nimitz-class scripting machinery of autoconf/autogen/automake
apparently always refrains
for me to spur to my commands on any system not identical with a
particular flavor of JBLD
(Joe's Bloated Linux Distribution)...